Page Two THE MICHIGAN DAILY - Friday, October 22, 1971 U- IN FOCUS Fine points of filters Al .t coming . . . for HALLOWEEN sensational black & white .--3D-- I spectacular COLOR by Richard Lee Q. What are the most useful filters? - Steve T. A. Depends on what your ob- jective is. It might be simpler if this column first attempts to explain abot light and filters in gen- gral. When white light falls on an object, the object first changes the structure of the light by absorbing all colors but its own, and then reflects back its own color. Subtraction is the key. A red apple, for example, re- flects back red, therefore by subtraction blue and green are absorbed. Breaking white light into its three primary colors of red, blue, and green, the yellow that the eye perceives is usually formed by a combination of red and green light. For example, a yel- CORRECTION In Tuesday morning's paper, The Daily reported that tic- kets for the homecoming con- certs were sold out. This is not true, and tickets are still on sale in the Union and at Sal- vation records. The Daily re- grets the error. low flower reflects back red and green, but absorbs blue. Filters operate in a very sim- ilar fashion. The color of the glass indi- cates which colors pass through to the film. And the principle of subtraction indicates w h i c h colorsare partially or totally held; back. A simple rule to remember is that filters transmit (or pass) their own color, absorb (or hold back) part or all of other colors. A RED filter transmits red, but absorbs blue and green. A GREEN filter transmits green,.but absorbs red and blue. A YELLOW filter (red p u s green) transmits red and green, but absorbs blue. The strength of the filter in- dicates how much of a particular color or set of colors is absorbed. There are two main reasons for the use of color filters for black and white filming. One of them is to correct the imperfect color sensitivity of the film, and make it translate the subject into tones of gray of more or less the same bright- ness as the colors appears to the eyes. Such filters are called cor- rection filters . The other reason is to distort (brighten or darken) the repro- duction of certain colors for special effects by using filters of deeper colors than for tonal cor- rection. Nearly all the black and white film generally used is panchro- matic innature indicating that the. film is sensitive to all visi- ble light, as well as to invisible ultra-violet radiation. The human brain perceives a yellowish-green color as t h e greatest visual stimulation in daylight. Pan film, on the other hand, is comparatively more sen- sitive in the blue-violet region. Hence, a yelow filter that will absorb blue, but transmit the red and ,green of the spectrum will be the filter to use for cor- recting colors to their p r o p e r gray scale tonal relationship. This is true only of outdoor scenes though, because then the source of illumination, usually the sun, is white light. .When you shoot indoors, the source of illumination is in all probability a tungsten light bulb, which emits a much warm- er light than the midday sun. The correction filter here is a light green filter. Apart from acting as a cor- rection filter for proper gray tonal reproduction of outdoor scenes, a yellow filter is most often used because it absorbs the blue of the sky, darkening it, thereby causing a greater se- paration of the white clouds, while still retaining the proper tone of faces. For a stronger effect, a deeper yellow or orange filter has to be used. This of course, should be used only for special effects as it distorts face tone, render- ing it chalky white. Using a red filter would make the sky ap- pear almost black, but face tone would be washed out, almost pale. Red lips in this case would be deathly white/ Most undesir- able, if the scene includes peo- ple, but for a stunning pictorial landscape, the red filter is very essential. Combined with a pol- arzing filter, you might e v e n create a prize winning landscape photo. Using a filter requires an in- crease in exposure time or f- stop. If you have a built in through the lens light meter, the exposure correction will be tak- en care of automatically, in most cases. If you're using a separate hand held exposure meter, you'll have to adjust for the filter being used. All filters have a filter factor engraved on the rim. This fac- tor is usually expressed as 2x, 3x, or whatever-x. A 2x factor means you divide your film's ASA number, for example Tri-X at 400, by 2. The quotient is 200. This number then is the ASA you get when using Tri-X rated normally with a 2x filter. So you now set your hand held me- ter to read exposures with a ASA film rating of 200. As previously noted, do not do this if your meter is a through the lens type. Just set it at the regular ASA 400, or whatever the film's normal rating is, and the meter will automatically compensate for the reduced amount of light reaching it af- ter passing through the filter. Q. How about a UV or Sky- light filter for use with black and white as well as color film? A. Most photographers look upon these type of filters as a cheap way of protecting their precious and expensive lenses from getting dusty, and heavens forbid, scratched! Because a UV or Skylight fil- ter is colorless, it requires no increase in exposure - o n c e screwed into the lens, you can practically forget its presence and sleep more peacefully. Q. What's the difference be- tween a UV and a Skylight fil- ter? A. Both absorb ultra-violet radiation but the skylight filter will also absorb a bit of the blue and green while the UV filter will only absorb the blue with little effect on the green. Both filters are recommended when shooting color portraits in open shade, and the use of either filter will add warmth to the scene. The UV filter, being a very very pale yellow in color warms the scene by throwing a very pale yellow cast. The Skylight filter on the other hand is very pale pink in color, so the very slight color cast is pinkish. Does that mean if you use it with color film, people will turn out with yellow or reddish faces? No. Because most color films, especially Kodak's Ektachrome is sort of biased towards blue, so the use of either of these filters will just correct or add warmth back to the scene. Also as mentioned, light in the open shade, in high altitudes or snow scenes, is excessively blue, so the use of these filters once again just corrects for the blue- ness. If you shoot in normal sun- light, it will add warmth to the scene. Complexions will come out looking healthy. It is also recommended for use with color film when shooting with electronic flash, because most strobe lights are cold, i.e., biased towards the blue. How- ever, a few of the newer strobes have a yellow-pink cast so as to warm the inherently cold quality of electronic lights. If a UV or Skylight filter is used in com- bination with this type of flash, the result might be a bit warm- er than desired. But it's all a matter of taste. Obviously there are more filt- ers made than can be described in this column; like color con- version filter, color balancing filters, contrast blue filters, po- larizers, diffusers, split focus, close-ups etc. For further in- formation on the subject, con- sult Kodak's "Filters for Black- and-White and Color Pictures". Here's some information on the UAC sponsored Photography Contest. There will be two categories, one for black and white, the other for color. Minimum print size is 5x7, while the maximum size is 20x24. All prints must be mounted. Entries can be submitted to the UAC office in the Union from Nov. 8-11. Photographs will be displayed in the Graduate Library from Nov. 15th to Dec. 3rd. Total prizes amounting to $100 are being donated by UAC and Purchase Camera Shop. Entry forms may be picked up from the UAC office beginning Oct. 27th For further informa- tion, call 763-1107. eyes of hell "In the gruesome division, this one is really very good."-L.A. TIMES fri.-sat., oct. 29-30 Natural Science Aud. 7:30-9-10:30 ARM 761-7849 G.B. SHAW Caesar an Cleopatra OCTOBER 20-23; Curtain at 8 P.M.! Box Office opens at 12:30 UNIVERSITY PLAYERS-POWER CENTER U I AUDITIONS FOR ANN ARBOR CIVIC THEATER PRESENTATION OFJ FIDDLER ON THE ROOF will be held from 1-5 p.m. for characters from 7-10 p.m. for ensemblej SUNDAY, OCT. 24-201 Mulholland Dr. ' t (Ensemble call-backs 7-10 p.m. Oct. 26) ( C(C haracter ca ll-backs 1-5 p .m . O ct. 30 ) Friday and Saturday GRAPES OF WRATH (1940) based on JOHN STEINBECK'S novel, directed by JOHN FORD with HENRY FONDA, JANE DARWELL and JOHN CARRADINE Merle Haggard's favorite movie SHOWN AT 7 & 9 Aud. A, Angell Hall x i I 'I I S Cameras. .Projectors i 0%/ 0 ALL NEW MERCHANDSIE - Some Slightly Scratched Great Buys - 1 Year Warranty - Limited Quantity. Bring This Ad and Save an additional $5.00 We Service all makes and models--Cameras and Projectors //upot Caftin 4a en'ice, S.. ... SHOP TONIGHT UNTIL 9:00 8005 Main St., Dexter Phone 426-4584 MD ___.__. I - . I . - - . . - DIAL 8-6416 TONIGHT NOW SHOWING AT 7-9 P.M. . ( f : 4 .: Ki2 "AN IMAGINATIVE, V I S UA L, BRUTAL ASSAULT ON THE SENSES.A TURBULENT MOVIE ONSLAUGHT!" -CUE MAGAZINE I E VANESSA REDGRAVE FINAL DAYS OLIVER REED Miss J glories in the softness of our Lanz dress for big doings this fall. It's cream cotton velour and brown cotton suedecloth with an embroidered midriff between. . .very soft and pretty. 5-13 sizes. A' in Ken Russell's Controversial Masterpiece Tc~i 14 't $38. Y 0%aJ~j III (FiF(O1'"H Forum FIFTHAVNUE AT LIBERTY liii pOWNTOWN ANN ABOR LJLJ INFORMATION 761.9700 FRI. 7-9-11 SAT. 5-7-9-11 V tAT JL V IM "ATIMPF nMi Y .. I A T IA II u IML